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Have you thought of trying intermittent fasting?

June 4, 2010

Well, have you?  I’m going to try and give you a couple of reasons to at least try it.  I do 1 or 2 24 hour fasts each week.

What is IF, you ask?  Well, it is the act of abstaining from food(calories to be more precise), most simply.  It can take many forms, such as the “20/4 rule” where every day consists of 20 hours fasting and a 4 hour feeding window.  There’s also alternate day fasting, which is, well, what it sounds like.  I’m currently at hour 16 of a 24 hour fast, and feeling great.  Oh, and I worked out for about 2hours 45minutes last night.

Although I don’t agree with all of his assumptions on metabolism/weight loss(e.g. “it’s all about calories in vs. calories out”), Brad Pilon wrote a very helpful book called Eat Stop Eat.  He does a great job presenting relevant research with regard to fasting and metabolism. For instance:

*Fasting will NOT slow your metabolism or cause you to waste muscle (based on 72 hour fasting study).

*Fasting doesn’t cause low blood sugar.  I might add a few things here: some people do in fact have “clinical hypoglycemia”.  Now this could simply be from a diet rich in carbohydrates, thus elevated circulating insulin levels, thus lowered blood sugar when carbs are not readily available.  In any case, the “symptoms” associated with fasting improve drastically over time, and if you’ve been eating primal/paleo, you shouldn’t have any problems, as you’re most likely keto-adapted to some degree

*Fasting will lead to many other hormonal/metabolic changes: reduction in circulating insulin levels, increased norepinephrine, epinephrine, glucagon and growth hormone levels.  These results are accentuated with resistance training in the fasted state.  My own anecdotal 2 cents: working out in the fasted stated dramatically reduces/eliminates hunger for several hours.

Remember, Insulin is the trump card which will overrule the ability of those other 4 hormones to liberate fat stores (the body’s preferred source of energy! otherwise why would we store it in that form!).

As an endurance athlete (at least until Ironman is over:) I like studies such as this which detail benefits of calorie restriction and IF on cycling endurance performance and body composition.

So, for me, it’s one or two 24 hour fasts each week, and on other days, I simply eat when I’m hungry, which may sometimes mean that my first meal is not until 12-3pm, an automatic IF of approx. 16-18 hours each day.  It has become effortless, my energy levels are steady, and I am actually more creative and productive on fasting days.  Try it and let me know how it goes!


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  1. carrie permalink

    So does this mean no coffee too? Or black coffee? because I’m assuming if you drink the coffee with cream, you’re certainly not fasting, right? I’ve thought about doing this. For some reason, fasting is a little scary for me…the “Ive got low blood sugar” issue..though I doubt I have it anymore. I’ll give it a try and let you know 🙂

    • Daniel Gregory permalink

      ohhhhh no coffee is certainly still in, sans cream. i never thought hunger could be a pleasant feeling until i started doing this.

  2. Fasting is also good if you are a mystic. I’ll be a mystic, you can be an Ironman. Best wishes on your event!!

    • Daniel Gregory permalink

      agreed. however, i’d be lying if i said i haven’t had some serious visions (read: hallucinations) on some of these long workouts:)

  3. TrailGrrl permalink

    That is sort of what I do… eat when I am hungry, which usually means my first meal of the day is well into the afternoon. Unless I ate crap the day before or ate dinner earlier than normal. Then I am hungry sooner.

    I too am a reformed triathlete. I picked up a copy of Triathlete mag at the store yesterday (which I subscribed to for years) and was browsing it and now I am like God, why did I ever want to do an IM? My view of the women’s and men’s bodies has changed dramatically. I used to think they looked really fit, but now I’ve noticed how “stringy” the women’s muscles look, and that the men are really sort of not as buff as I thought but sort of scrawny. Nice legs, though.

    I got so into “training” that I started to hate all three sports (lap swimming does pretty much suck). And the injuries and visits to the orthopod, the chiropractor, the massage therapist. I had bad plantar fasciitis after I did Flying Pig marathon the first time they had it in 1999 and then had piriformis from cycling and running. I found some stuff about barefoot running and MovNat and started doing that as well as working out at a non-traditional place with tire flipping and sled pulling and sledgehammers. I only trail run now and use VFF’s (completely barefoot on the mulchy stuff was a splinter nightmare, but I love it on real dirt) and keep it to around a half hour or less.

    Totally revamped eating starting with Real Food by Nina Planck and moving into primal/paleo pretty much. No more gels, electrolyte drinks, or protein shakes. Stopping or cutting back on wheat and dairy got rid of all sorts of GI problems and a feeling of being bloated up.

    People ask if I am working out a lot or training for something because I have dropped about 3-4 sizes over the course of 2 years and have maintained it. I tell them no, not really (honestly, I go for weeks without working out at all). I love stretch bands, kettlebells, and now have a supension trainer. But the outdoors is my favorite workout. I used to be in a tizzy to see the health club facilities when I was on travel but now I scope out places where I can do bodyweight stuff or run (even a small patch of dirt is fair game for me to consider it a “trail”). Not having this idea of “training” for an event in order to get in shape has really freed up a lot of time and energy. No more worrying about what you are supposed to be doing. And you can do a lot of rounds of quality bodyweight and band stuff in about 15 minutes and feel it in your pecs the next day. I spent a whole lot of money on trainers and supplements and found out that I needed to take ownership of my health and fitness.

    Now I see it as something to enjoy and do because I want to be fit to help myself and others, not to lose weight or look good necessarily. I used to totally sugar-out and not be able to go without eating for more than a couple of hours.

    There is a nice pool at my dad’s community and it is looking mighty inviting now that I think of jumping in and swimming around and going underwater to play instead of to swim laps.

    I would like to spend more time on my bikes this summer, both mountain and road bikes. Once you don’t worry about going a certain speed, you can enjoy the view of the river.

    Out of curiosity, what are you eating on longer rides?

    Great blog!


  4. you can really learn a lot from health clubs specially if there are doctors who are also members on the health club ..~


    • Daniel Gregory permalink

      Lee, I’m not sure what you’re asking. Good luck with the plantar fasciitis…I’ve known several people who experienced improvements by ditching supported shoes with raised heels.

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